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Dinosaur Eggs

Just as fossils provide important information about life-forms that inhabited our world in the distant past, the rocks that they are preserved in constitute our only evidence to interpret when these ancient animals lived. To recount this part of our investigation, we need to flash back from the lab to the field. What originally attracted us to explore the site that contained the eggs and embryos in Patagonia was the stunning visual beauty of the area's rocky outcrops. Layer upon layer of...

Just as modern investigators must often return to the scene of an accident to gather more evidence after their initial investigation, we also needed to reexamine the site of our discovery. There were still many mysteries about how the sauropods had laid their eggs Did they lay them in discrete nests or scatter them randomly across the surface of the floodplain If they were in nests, how many were laid at one time Did all the eggs belong to one sauropod species, or did multiple species use the...

The most common components of dinosaur research are the discovery of previously unknown species and the analysis of their diversity and evolutionary history. Other important biological components are the study of how dinosaurs changed through time, as well as how they moved and behaved. These intriguing scientific investigations, however, must be founded on a clear understanding of the genealogical relationships of each species. Without knowing the origin of each group, which represents the...

We arrived back in New York during the first week of December 1997. As detailed in our collecting agreements, Rodolfo and his museum in Plaza Huincul gave us permission to borrow several of the fossils we had collected so that Marilyn could prepare them at the Peabody Museum at Yale University and Luis could study them at the American Museum of Natural History. At the same time, Rodolfo and Sergio planned to prepare some of the other blocks of eggs at the Carmen Funes Museum. Our initial task...

To figure out what had killed all the unhatched sauropods in the eggs, we again had to appeal to the rocks that contained the fossils. In addition to providing the only direct evidence to estimate the time of the embryos' death, the picturesque layers of rocks at Auca Mahuevo preserved key clues for interpreting the cause of their death, which appeared to be directly related to the environment in which the sauropods had laid their eggs. The evidence for interpreting what environment the...

Dinosaur eggs have been found on all continents except Antarctica. Among the oldest are those associated with the tiny prosauropod hatchlings of Mussasaurus from the late Triassic of South America. The few known late Jurassic sites are restricted to North America, Europe, and Tanzania. Eggs from the early Cretaceous are far more abundant, but with the exception of one site from southern Australia, all are restricted to the Northern Hemisphere. Although a large number of late Cretaceous sites...

Some animals are gregarious, whereas others live more solitary lives. How did the giant sauropods behave, especially when they went to the nesting site at Auca Mahuevo to lay their eggs It had previously been suggested that sauropods laid their eggs in enormous colonies. The studies of the Indian and Pyrenees egg sites, mentioned in the last chapter, documented that thousands of eggs had been laid in areas encompassing several square miles. To the paleontologists studying those sites, this...

Adult skeletons of dinosaurs are not that uncommon because their massive bones and durable enamel teeth stand a reasonable chance of becoming fossilized. Finding the fragile bones and skin of unhatched dinosaurs is much more rare, however, because their poorly calcified bones and delicate skin decompose rapidly after the embryo dies. At the time of our discovery, in fact, fossilized embryos were known from only a handful of different dinosaur species, despite hundreds of species having been...

In November of 1998 just before Thanksgiving, two articles about the nesting site at Auca Mahuevo announced what we had found. One was the scientific paper in Nature the other was a popular article that was published in National Geographic. The National Geographic Society had helped to fund our 1997 expedition, and they wanted to let the public know what we had found. To let other media outlets know about the discovery, we also scheduled a news conference at the American Museum of Natural...

With two successful expeditions to Auca Mahuevo, we had learned a lot about the reproductive behavior of sauropod dinosaurs, but many questions still remained open What kinds of sauropods were responsible for these amazing nesting seasons Could we find evidence to fine-tune our identification of them Was the egg-clutch distribution of the extensive egg layer 4 comparable to the highly concentrated and randomly distributed clutches from egg layer 3 Were the sauropods laying their eggs in natural...

Nature has preserved a priceless window on the past for us at Auca Mahuevo. As a result of our crew's discoveries and investigations, it has become possible to peer through that window and envision some of what life was like 80 million years ago on the plains of Patagonia. The vision that has emerged is breathtaking, and if it were possible for us to drop in for a visit, it would be difficult for us to recognize where we were. Huge herds of lumbering sauropods more than forty feet long roamed...

Our primary goal in undertaking the second expedition was to gain a better understanding of the reproductive behavior of sauropods. Given the evidence that was preserved in the rocks at the site, the answer to one aspect of this behavior had become clear. Many modern animals return to the same area to lay their eggs during different breeding seasons. Did the ancient giant dinosaurs of Patagonia do this also The evidence to answer this question was in the stratigraphic section that showed all of...

During the last week of October in 1997, Suzi Zetkus and Luis flew from New York to Buenos Aires to buy the rest of the supplies we needed and to rent a van for transporting the gear and crew into the field. Lowell and the rest of the crew flew down during the first week in November, and we met several students and scientists from universities and museums in Argentina who would also be part of our expedition. After completing the shopping for the last items on our list of supplies, we were...

One might think that being fifty feet long and weighing several tons would make adult sauropods, such as those that lived around Auca Mahuevo, quite invincible. But a pilgrimage to the nesting site at Auca Mahuevo was clearly not without risks, even for giant sauropods and their offspring. Fearsome predators roamed the floodplain. During the first expedition to Auca Mahuevo, no skeletons of adult dinosaurs were found at the nesting site despite several efforts to find some. That we had found...